The effect of deer browsing on wheat yield

Bowman, Jacob L.White-tailed deer (Odocoileus virginianus) are overabundant in many areas of the country and increased deer numbers have caused damage to agronomic crops to increase. Winter wheat (Triticum aestivum) is a commonly grown crop and food source for white-tailed deer on the Delmarva Peninsula. The effect of deer browsing on corn and soybean yields has been documented, but research is lacking on the effect of deer browsing on wheat yield. In 2007-2009, I investigated the effect of browse timing and wheat type (bearded and unbearded) on wheat yield in Delaware. I placed 1680, 4.4 m2 plots in the middle of 10 m distance classes starting from the forested edge out to 60 m. In 2007, I systematically assigned 1 of 2 treatments (i.e., no protection or protected at planting) to the plots. In 2008-2009, I added a third treatment: protected prior to heading. After head emergence, I conducted weekly browse surveys on all unprotected plots to determine browse rates. I collected weekly biomass samples to estimate the amount of wheat biomass removed by deer. I harvested a 1 m2 area in the middle of each plot to determine the deer impact on yield. I also tested if browsing affects the test weight of wheat during 2008 and 2009. Browsing increased in intensity as head development progressed with most browsing occurring on the unbearded wheat. I found no interaction between wheat and treatment (P > 0.10) during the study. Unprotected plots yielded 195 kg/ha more wheat then protected plots in 2007 (P = 0.08). I found no difference between treatments for 2008 and 2009 (P = 0.38). Bearded wheat yielded 379 kg/ha higher in 2007 and 399 kg/ha higher in 2008 and 2009 than unbearded wheat (P < 0.001). I found no difference in test weight among treatments (P = 0.42) or between wheat types (P = 0.997) in 2008 and 2009. My browse surveys demonstrated avoidance of bearding but the overall browsing was not intense enough to reduce yield. My results differed from past research documenting a reduction in yield but the lower deer density (~15 deer/km2) on my study area was the likely cause of the difference.University of Delaware, Department of Entomology and Wildlife EcologyM.S